A typical network includes multiple nodes that communicate with one another over a path through the network. The path often extends over multiple nodes, and includes at least one optical connection for connecting two adjacent nodes. A node that originates information, or a source node, can compute the path and set up appropriate optical connections using a known Optical Signal and Routing Protocol (OSRP), and information can be exchanged between nodes in accordance with a Synchronous Optical Network (SONET) protocol. SONET is the ANSI (American National Standards Institute) standard for transmitting information over optical fiber. The optical connection may be a Sub Network Connection (SNC), which is a collection of one or more SONET paths or SDH (Synchronous Digital Hierarchy) paths. The SONET standard is used in the United States and Canada and is a variation of the SDH standard. SDH is the ITU-TSS (International Telecommunications Union—Telecommunications Standards Sector) international standard transmitting information over optical fiber. More particularly, an SNC is a connection from a node in a separately identifiable part of a larger network to another node in the networks and typically spans multiple nodes and links. As part of an SNC creation, switching paths are created along the nodes that are traverse by SNC, thus enabling data to flow from the originating node to the destination node. In other words, an optical network can be partitioned into a set of optical sub-networks interconnected by optical links, and the SNC is a connection across an optical sub-network.
FIGS. 1A and 1B illustrate the “Mesh Restoration” method which is a conventional method for performing SNC recovery in response to a failure on an SNC because of an OSRP line failure. Assume that prior to an SNC failure, the traffic flow 105 is along a path formed between source node 100A, intermediate node 100D, destination node 100C, and lines 106 and 107. There will be a failure on the SNC when an OSRP line fails. For example, in FIG. 1, assume that the OSRP line 107 between nodes 100D and 100C fails. If there is a failure on the SNC because of an OSRP line failure, then a signaling message is sent to the source node 100A so that the failed SNC is released to the source node 100A. Releasing an SNC results in all switching paths to be torn down along all the nodes and links that are traversed by the SNC. This results in the immediate stoppage of the flow of data along the released SNC. The source node 100A then calculates an alternate path, sets up the SNC for the alternate path, and signals the rerouted SNC information to the destination node 100C. In the example of FIG. 1a the traffic flow 105 is now along a path formed by node 10A, node 100B, node 100C, and lines 111 and 112, after Mesh Restoration is performed.
The conventional Mesh Restoration method has a restoration time that is highly dependent on the number of hops (distance between intermediate network points) that are traversed by the SNC. The SNC restoration time disadvantageously increases as the average number of nodes in the path of the failed SNC increases. For example, if there is a high number of hops (e.g., 3 hops or greater) that are traversed by the SNC from the source node to the destination node, then the amount of time to perform the SNC recovery and the reset of the line connections will be longer, since the SNC release and new SNC setup will involve the source node. Therefore, the Mesh Restoration method can have performance disadvantages.
The Mesh Restoration method also involves the following activities: (1) transmission of signaling messages to the source node and to the destination node via the alternate path, (2) transmission of routing messages to update the state of the network during and after SNC restoration; and (3) transmission of node management events from the nodes on the network paths (affected by the SNC restoration) to management stations, in order to provide the status of the SNCs. These various activities limit the scalability of the nodes. Furthermore, the scalability of management stations is dependent on the number of generated events, and a high number of generated events can limit the scalability of the management stations.
Therefore, the current technology is limited in its capabilities and suffers from at least the above constraints and deficiencies.